1. Field of the Invention
The invention relates to a circuit board and, more particularly, to a circuit board for an electronic device.
2. Description of the Prior Art
Referring to FIGS. 1 and 2, FIG. 1 is a partial sectional view illustrating an electronic device 1 of the prior art, and FIG. 2 is a top view illustrating the circuit board 14 shown in FIG. 1. As shown in FIG. 1, the electronic device 1 comprises a top casing 10, a bottom casing 12 and a circuit board 14 disposed between the top and bottom casings 10 and 12. As shown in FIG. 2, the circuit board 14 comprises a main body 140, a plurality of electronic components 142 and a plurality of fixing portions 144. The electronic components 142 and the fixing portions 144 are disposed on the main body 140. In general, the fixing portion 144 is made of metal. In practical applications, the electronic components 142 can be central processing unit (CPU), north bridge chip, south bridge chip, Complementary Metal-Oxide-Semiconductor (CMOS), graphic card and so on, and will generate heat while being operated for a span of time.
As shown in FIG. 1, the top casing 10 has a fixing portion 100 including a plastic protrusion and a metal nut (not shown) disposed therein, and the bottom casing 12 has a fixing portion 120 including a plastic protrusion and a metal nut (not shown) disposed therein. A fixing member 16 (e.g. screw) can pass through the fixing portion 120 of the bottom casing 12, the fixing portion 144 of the circuit board 14 and the fixing portion 100 of the top casing 10 so as to fix the circuit board 14 between the top and bottom casings 10 and 12.
When the electronic device 1 is working, heat generated by the electronic components 142 is transferred to the fixing portion 144 via the main body 140 and then transferred to the outside surfaces of the top and bottom casings 10 and 12 via the fixing portions 100 and 120. Consequently, the surface temperature of the electronic device 1 will get higher and higher and may exceed the standard temperature, such that the outer partial surface may get overheated.